1. Field of the Invention
This invention relates to a head for grasping and guiding a length of pipe, such as marine riser pipe, particularly to stabilize the length of pipe when suspended by a cable secured to a derrick hook and to one end of the length of pipe.
2. Description of the Prior Art
U.S. Pat. No. 3,561,811, issued Feb. 9, 1971, J. W. Turner, Jr., "Well Pipe Racker" discloses pipe handling equipment associated with the derrick of a well drilling ship. The lowermost pipe handling assembly of the Turner patent is described as casing manipulating apparatus.
Marine riser pipe is pipe of large diameter that extends from well head equipment on the floor of the ocean up through the water and terminates above the surface of the water within the moon hole of a drilling ship. The drill string is lowered through the riser pipe into the well therebelow when the well is being drilled. Small diameter control lines are secured longitudinally along the exterior of the riser pipe, and the riser pipe may be covered with a resilient flotation or buoyant material which also covers the control lines. Casing may also be run through the riser pipe.
The riser pipe is made up of convenient lengths that are coupled together. When running riser on a drill ship, the riser lengths are hung by a length of cable from the hook of the hoisting equipment with the lower end of the riser length hanging free. Owing to the motion of the ship, the lower end has a pendulum action which is dangerous to men and equipment.